JP6959194B2 - Hot water supply device and control method of hot water supply device - Google Patents

Description

The present invention relates to a hot water supply device and a control method for the hot water supply device.

The heat pump type hot water supply device consists of a heat pump unit for boiling hot water and a hot water storage unit for storing the hot water. The heat pump unit consists of a compressor, a water-refrigerant heat exchanger, a decompression device, and an air heat exchanger, which are connected in an annular shape. During the boiling operation, the air heat exchanger operates as an evaporator. Therefore, when the outside air temperature is low and the humidity is high, frost may adhere to the air heat exchanger, the boiling capacity is lowered, and energy saving is impaired. Therefore, a defrosting operation for removing frost from the air heat exchanger is required.

As a means for determining whether or not the defrosting is necessary, Patent Document 1 utilizes the outside air temperature and the air heat exchanger outlet temperature to lower the air heat exchanger outlet temperature below a reference temperature, which is a predetermined temperature lower than the outside air temperature. If the temperature becomes low, it is judged that defrosting is necessary, and defrosting operation is performed.

Japanese Unexamined Patent Publication No. 2003-222392

However, since the outside air temperature thermister is provided outside the heat pump unit, if snow or ice adheres to the outside air temperature thermista, the temperature difference from the air heat exchanger outlet temperature cannot be taken correctly. Therefore, in the case of the above method, air is used. Even if frost adheres to the heat exchanger, there is a risk that the defrosting operation cannot be performed.

The first invention made in view of the above circumstances is
A hot water preparation unit having a hot water storage tank, a pipe connecting both ends to the hot water storage tank, and a pump for sending cold water from one end side to the other end side of the pipe.
A compressor that compresses the refrigerant, a water-refrigerant heat exchanger that exchanges heat with the cold water, a decompression unit that decompresses the heat-exchanged refrigerant, and air heat that exchanges the decompressed refrigerant with air. With a switch, with a cycle,
A hot water supply device including a radiator outlet temperature sensor that detects the outlet temperature of the water-refrigerant heat exchanger.
When it is detected that the detection temperature of the radiator outlet temperature sensor starts to decrease, the decrease speed decreases, and then the temperature starts to increase, the air heat exchanger is based on the transition of the detection temperature of the radiator outlet temperature sensor. It is characterized by performing defrosting.

(Reference example)
In addition, the second invention made in view of the above circumstances
A hot water preparation unit having a hot water storage tank, a pipe connecting both ends to the hot water storage tank, and a pump for sending cold water from one end side to the other end side of the pipe.
A compressor that compresses the refrigerant, a water-refrigerant heat exchanger that exchanges heat with the cold water, a decompression unit that decompresses the heat-exchanged refrigerant, and air heat that exchanges the decompressed refrigerant with air. With a switch, with a cycle,
A method for controlling a hot water supply device having a radiator outlet temperature sensor for detecting the outlet temperature of the water-refrigerant heat exchanger.
An initial operation in which the compressor is driven with the expansion valve open, the pump is driven to start sending cold water to the water-refrigerant heat exchanger, and then the opening degree of the expansion valve is reduced. Steps and
A normal operation step for maintaining the rotation speed of the compressor and the opening degree of the expansion valve substantially constant, and
A frost formation step that increases the number of revolutions of the compressor and / or decreases the delivery flow rate of the pump.
The defrosting step of increasing the rotation speed of the compressor and / or increasing the opening degree of the expansion valve is performed in this order.

Overall configuration diagram of the hot water supply device of the first embodiment The cycle diagram shown on the Moriel diagram of the hot water supply device of Example 1. Temperature chart of the hot water supply device of Example 1 Control flowchart of defrosting operation of hot water supply device of Example 1

Hereinafter, examples of the present invention will be described with reference to the accompanying drawings. The various components of the present invention do not necessarily have to be individually independent, for example, one component may consist of a plurality of members, a plurality of components may consist of a single member, or a certain component. Allows duplication of some of the components with some of the other components.

FIG. 1 is an overall configuration diagram of the hot water supply device of this embodiment.
The hot water supply device includes a heat pump 100, a hot water preparation unit 101, and a control device 11 for controlling these.
[Thermodynamic cycle]
The heat pump 100 includes a compressor 1 that compresses the refrigerant, a water-refrigerant heat exchanger 2 that dissipates heat by exchanging heat of the compressed high-temperature refrigerant with the water in the hot water storage tank 12, an expansion valve 3 that expands the dissipated refrigerant, and so on. The evaporator 4 that evaporates the expanded liquid refrigerant is connected in a ring shape as a heat cycle. The evaporator 4 is arranged so as to be heat exchangeable with the outside air.

A discharge temperature sensor 7 for detecting the refrigerant discharge temperature of the compressor 1 is arranged between the compressor 1 and the water-refrigerant heat exchanger 2. By reducing the opening degree of the expansion valve 3 as the detection temperature of the discharge temperature sensor 7 increases, the cycle COP (Coefficient Of Performance) of the heat pump 100 can be made suitable.
The evaporator 4 is provided with a fan 6 that promotes heat exchange with the outside air. Further, a water entry temperature sensor 9 for detecting the temperature of cold water sent to the water-refrigerant heat exchanger 2 by the pump 5 is arranged. A radiator outlet temperature sensor 20 for detecting the refrigerant temperature after heat dissipation is provided between the outlet of the water-refrigerant heat exchanger 2 and the expansion valve 3. Further, the hot water temperature thermistor 10 for detecting the temperature of the hot water exchanged by the water-refrigerant heat exchanger 2 is provided.

[Hot water preparation unit 101]
The hot water preparation unit 101 has a hot water storage tank 12, a water supply pipe for supplying water to the lower end side of the hot water storage tank 12, and a hot water supply pipe for taking out hot water from the upper end side of the hot water storage tank 12. Further, from the lower end side of the hot water storage tank 12 to the upper end side of the hot water storage tank 12 through the water-refrigerant heat exchanger 2, a pipe through which hot water can pass is connected, and the hot water storage tank 12 and the water-refrigerant heat exchanger 2 are connected. A pump 5 for sending water from the hot water storage tank 12 to the water-refrigerant heat exchanger 2 is arranged between the hot water storage tank 12 and the water-refrigerant heat exchanger 2.

[Changes in refrigerant due to thermal cycle]
FIG. 2 is a Moriel diagram of the hot water supply device of this embodiment.
Since the refrigerant is compressed in the compressor 1, the refrigerant pressure increases and the enthalpy slightly increases due to the compression work received from the compressor 1. Therefore, the refrigerant travels toward the upper right in the Moriel diagram by the compressor 1 (compression process).

Further, since the refrigerant dissipates heat in the water-refrigerant heat exchanger 2, the enthalpy of the refrigerant is reduced. Therefore, the refrigerant travels to the left in the Moriel diagram by the water-refrigerant heat exchanger 2 (heat dissipation process).

Further, in the expansion valve 3, the refrigerant expands and the pressure decreases. Therefore, the refrigerant travels downward in the Moriel diagram by the expansion valve 3 (expansion process).

Further, in the evaporator 4, the refrigerant exchanges heat with the outside air. Normally, the temperature of the refrigerant in the evaporator 4 is lower than that of the outside air, so that the refrigerant absorbs heat by the evaporator 4 and the enthalpy increases. Therefore, the refrigerant travels to the right in the Moriel diagram by the evaporator 4 (evaporation process).

[Temperature fluctuation at each location as control progresses]
FIG. 3 is a diagram showing the passage of time between the water-refrigerant heat exchanger 2 outlet temperature and the water inlet temperature of the hot water supply device of this embodiment. The control device 11 commands each of the following controls. The hardware structure of the control device 11 is not particularly limited as long as each control can be executed. For example, the control device 11 can be a command device provided separately from the arithmetic unit such as a CPU incorporated in the thermal cycle and the thermal cycle. ..
(Initial operation)
When the water heater starts boiling water, first, the compressor 1 is preferably driven at a constant speed with the expansion valve 3 open, and the pump 5 is driven to drive the water-refrigerant heat exchanger 2 into the hot water storage tank 12. Supply water. As a result, the compressed high-temperature refrigerant passes through the water-refrigerant heat exchanger 2, so that the temperature of the radiator outlet temperature sensor 20 (“water heat exchange outlet refrigerant temperature” in FIG. 3) begins to rise sharply.

Next, when the expansion valve 3 is gradually closed, the flow rate of the refrigerant circulating in the heat cycle decreases, but the amount of enthalpy dissipated by the water-refrigerant heat exchanger 2 does not fluctuate relatively. Therefore, since the amount of heat radiation of the refrigerant (the amount of decrease in enthalpy) per unit flow rate increases, the temperature of the refrigerant detected by the radiator outlet temperature sensor 20 decreases. Further, since the temperature of the water supplied from the lower part of the hot water storage tank 12 is relatively constant, the temperature difference between the radiator outlet temperature sensor 20 and the water inlet temperature sensor 9 becomes small.

When the blockage of the expansion valve 3 is advanced to the target value, the blockage of the expansion valve 3 is stopped. Then, since the rotation speed of the compressor 1 and the opening degree of the expansion valve 3 become (at least almost) invariant, the thermal cycle gradually stabilizes. Therefore, the temperature of the refrigerant detected by the radiator outlet temperature sensor 20 does not fluctuate relatively. That is, the temperature difference between the radiator outlet temperature sensor 20 and the water entry temperature sensor 9 is minimized.

(Normal operation)
After the above initial operation, by keeping the rotation speed of the compressor 1 and the opening degree of the expansion valve 3 substantially constant, a stable amount of heat can be supplied to the water-refrigerant heat exchanger 2. The cycle in the Moriel diagram in this case is drawn by a solid line connected by quadrangular plot points in FIG.
However, when the operation of the thermal cycle is continued, the evaporator 4 that exchanges heat with the outside air continues to maintain the temperature below the freezing point, so that it gradually frosts and is covered with frost.

(Operation at the time of frost)
When the amount of frost formed on the evaporator 4 increases, the contact area of the evaporator 4 with the outside air decreases, so that the amount of enthalpy given to the refrigerant through the evaporator 4 decreases. Therefore, as the frost forms, the Moriel diagram in the evaporation process shifts to the right. That is, since the area surrounded by the cycle decreases, it can be seen that the amount of work in one cycle decreases.

On the other hand, the endothermic amount Q obtained by evaporating the refrigerant in the evaporator 4 is obtained by multiplying the contact air amount F with the outside air and the temperature difference ΔT of the evaporator 4 generated by the endothermic heat by heat exchange. Since the amount of heat absorbed for the phase transition due to evaporation is constant, the temperature difference ΔT increases as the air volume F decreases as the contact area decreases. This indicates that the pressure at the start of the evaporation process decreases, so the points on the Moriel diagram at the start of the evaporation process transition downward. This increases the amount of work in one cycle, but is generally lower than the amount of enthalpy supplied to the refrigerant by frost formation. The cycle at this time is drawn by a broken line connected by triangular plot points in FIG.

Therefore, the cycle efficiency decreases as the frost formation progresses, and the amount of heat absorbed by the water on the hot water storage tank 12 side in the water-refrigerant heat exchanger 2 decreases. Therefore, in this embodiment, first, when the temperature drop of the hot water temperature sensor 10 is detected after the transition to the normal operation, it is determined that the cycle efficiency is decreasing, and the rotation speed of the compressor 1 is increased. As a result, the flow rate of the refrigerant increases, so that the amount of decrease in enthalpy per unit flow rate in the water-refrigerant heat exchanger 2 decreases, so that the temperature of the refrigerant detected by the radiator outlet temperature sensor 20 rises. Further, since the temperature of the water supplied from the lower part of the hot water storage tank 12 is relatively constant, the temperature difference between the radiator outlet temperature sensor 20 and the water inlet temperature sensor 9 becomes large.

That is, in this embodiment, the detection temperature of the radiator outlet temperature sensor 20 decreases by closing the expansion valve 3 after the start of driving the thermal cycle. After that, the blockage of the expansion valve 3 is stopped at a predetermined target value, and the compressor rotation speed is preferably substantially constant to shift to normal operation, and the change in the detection temperature of the radiator outlet temperature sensor 20 becomes small. After that, when the temperature drop of the hot water temperature sensor 10 is detected as the frost is formed, the detection temperature of the radiator outlet temperature sensor 20 rises in order to increase the number of revolutions of the compressor, and the water inlet temperature sensor 9 supplied from the hot water storage tank 12 increases. The difference from the detected temperature becomes large.

Instead of or in addition to increasing the number of revolutions of the compressor, the drive of the pump 5 may be weakened to reduce the amount of water supplied.

(Operation during defrosting)
In this embodiment, the detection temperature of the radiator outlet temperature sensor 20 drops, the temperature difference from the detection temperature of the water entry temperature sensor 9 becomes small, and the drop becomes gradual, that is, the radiator outlet temperature and the water entry temperature. Defrosting is required when the temperature difference from the radiator outlet rises after the temperature difference with the water enters is minimized (or minimized), and the temperature difference from the water entry temperature expands to a predetermined value (approximately 4 ° C to 5 ° C). Judging that, the defrosting operation is started.

During the defrosting operation, the defrosting operation is performed by supplying a relatively high temperature refrigerant to the evaporator 4 by maximizing the rotation speed of the compressor 1, for example, and opening the expansion valve 3 fully, for example.
As the defrosting progresses, the temperature of the refrigerant on the suction side also rises, so that the temperature detected by the radiator outlet temperature sensor 20 rises. In this embodiment, this increase is detected, and defrosting is terminated when a predetermined time elapses.

(Return operation)
After the defrosting is completed, the rotation speed of the compressor 1 and the valve opening degree of the expansion valve 3 are reduced to about the initial operation, and the operation from the initial operation to the normal operation is performed again.

[Control flowchart]
FIG. 4 is a control flowchart of this embodiment. _{After the start of operation, the difference ΔT now} between the detection temperature of the radiator outlet temperature sensor 20 and the incoming water temperature supplied from the hot water storage tank 12 is calculated at predetermined time intervals (step S11). After that, the difference between the detected temperature of the radiator outlet temperature sensor 20 one before _{ΔT now and the incoming water temperature supplied from the hot water storage tank 12 is compared with ΔT now-1} (step S12), and ΔT _now is ΔT. Determine if it is greater than _{now-1 (step S12').} If ΔT _now is _{smaller than ΔT now-1} , the process returns to step S11.

As shown in the temperature chart of FIG. 3, since the high temperature refrigerant passes through the water-refrigerant heat exchanger 2 after the heat pump unit is started, the temperature of the radiator outlet temperature sensor 20 starts to rise sharply. _{Therefore, the difference ΔT now} from the incoming water temperature supplied from the hot water storage tank 12 is large, but after that, the difference becomes small, and the difference becomes almost the minimum during normal operation. That is, the switching from the initial operation to the normal operation is determined by the difference between the radiator outlet temperature and the water entry temperature.

_{Replace ΔT now-1} with ΔT _min when the difference between the radiator outlet temperature and the water entry temperature is minimized (step S13), and set the correction value α as ΔT _min + β (however, β> 0) ( Step S14). After that, it is determined whether or not the difference between the radiator outlet refrigerant temperature and the incoming water temperature is equal to or greater than the correction value α set in step S14 (step S15). If frost formation progresses in the evaporator 4 and frost clogging occurs, as described above, the radiator outlet refrigerant temperature rises, and the difference between the radiator outlet refrigerant temperature and the incoming water temperature becomes large, which is corrected. The value is α or more. When the difference between the radiator outlet refrigerant temperature and the incoming water temperature is not equal to or greater than the correction value α, it is determined that the defrosting operation is not necessary (steps S15 and No), and the determination in step S15 is repeated. If the difference between the radiator outlet refrigerant temperature and the water entry temperature is the correction value α or more in step S15, it is determined that defrosting operation is necessary, and defrosting operation is performed (step S16).

During the defrosting operation, the high-temperature refrigerant from the compressor 1 flows into the radiator 2, so the radiator outlet temperature rises, and when the set value δ or more elapses for a predetermined time, it is determined that sufficient defrosting has been performed. (S17) and end the defrosting operation.

In this embodiment, the necessity of defrosting was determined by using _{the difference ΔT now} between the detection temperature of the radiator outlet temperature sensor 20 and the incoming water temperature supplied from the hot water storage tank 12, but the radiator outlet temperature sensor 20 It may be replaced with the detected temperature. However, since the detection temperature of the radiator outlet temperature sensor 20 is affected by the temperature of the water sent from the pump 5, for example, when the entire amount of water in the hot water storage tank 12 is to be pumped up, the water temperature is also affected at the final stage. The temperature is rising, and the temperature detected by the radiator outlet temperature sensor 20 is also rising. Therefore, apart from the timing of defrosting, there is a risk of erroneously detecting that defrosting is necessary even at the end of boiling, so it is preferable to use the difference value as in this embodiment.

1 Compressor 2 Water-refrigerant heat exchanger (heat sink)
3 Expansion valve 4 Evaporator (air heat exchanger)
5 Water supply pump 6 Evaporator fan 7 Discharge temperature sensor 9 Outside air temperature sensor 10 Outflow temperature thermistor 11 Control device 12 Hot water storage tank 20 Dissipator outlet temperature sensor 100 Heat pump 101 Hot water preparation unit

Claims (3)

A hot water preparation unit having a hot water storage tank, a pipe connecting both ends to the hot water storage tank, and a pump for sending cold water from one end side to the other end side of the pipe.
A compressor that compresses the refrigerant, a water-refrigerant heat exchanger that exchanges heat with the cold water, a decompression unit that decompresses the heat-exchanged refrigerant, and air heat that exchanges the decompressed refrigerant with air. With a switch, with a cycle,
A hot water supply device including a radiator outlet temperature sensor that detects the outlet temperature of the water-refrigerant heat exchanger.
When it is detected that the detection temperature of the radiator outlet temperature sensor starts to decrease, the decrease speed decreases, and then the temperature starts to increase, the air heat exchanger is based on the transition of the detection temperature of the radiator outlet temperature sensor. performing a defrosting hot water supply apparatus it said. A hot water preparation unit having a hot water storage tank, a pipe connecting both ends to the hot water storage tank, and a pump for sending cold water from one end side to the other end side of the pipe.
A compressor that compresses the refrigerant, a water-refrigerant heat exchanger that exchanges heat with the cold water, a decompression unit that decompresses the heat-exchanged refrigerant, and air heat that exchanges the decompressed refrigerant with air. With a switch, with a cycle,
A hot water supply device including a radiator outlet temperature sensor that detects the outlet temperature of the water-refrigerant heat exchanger.
It has an incoming water temperature sensor that detects the temperature of the cold water.
When it is detected that the difference between the detection temperature of the radiator outlet temperature sensor and the detection temperature of the water inlet temperature sensor starts to decrease and then starts to increase after the decrease speed decreases, the radiator outlet temperature sensor hot water supply apparatus you and the client performs defrosting of the air heat exchanger based on the transition of the detected temperature. The hot water supply device according to claim 1 or 2 , wherein the execution of defrosting ends after the detection temperature of the radiator outlet temperature sensor rises.

Images